EEVblog - 2014-06-13
Part 7 of Microphone Technology with Doug Ford, former head designer at Rode Microphones. This video Doug takes you through the design of the Rode NT3 and NT1000 microphone designs. There is a ton of stuff in here: Closed loop unity gain JFET and bipolar follow circuits. Bootstrapping out miller capacitance. JFET biasing. How to eliminate expensive high value resistors. How to add a bridged-T network to add marketing "pizazz" to a microphone. How to stop oscillation in closed loop systems. How to test and design closed loop systems for stability. Dominate pole compensation. Traps for young players in power amplifier stability. How circuits with capacitive loads oscillate. Emitter degeneration. Parasitic inductances and their effects. How to design a low noise and ultra high dynamic range valve based microphone preamplifier. Microphone power supplies. And how to design an amplified zener current source. All other videos in this series are HERE: https://www.youtube.com/playlist?list=PLvOlSehNtuHv98KUcud260yJBRQngBKiw Forum HERE: http://www.eevblog.com/forum/blog/eevblog-629-how-to-design-a-microphone-preamplifier/ EEVblog Main Web Site: http://www.eevblog.com EEVblog Amazon Store: http://astore.amazon.com/eevblogstore-20 Donations: http://www.eevblog.com/donations/ Projects: http://www.eevblog.com/projects/ Electronics Info Wiki: http://www.eevblog.com/wiki/
Damn this video just opened my eyes. I have a pair of NT3s, and i always hated that bump, and eq-ed it out. First thing in the morning i am getting my soldering station and getting that part of the circuit out. Thank you so much!
What a privilege to be able to watch an expert explain the reasoning behind their thinking. Excellent content!! Thanks Dave :)
This video is incredibly educational and well explained in such a way that I enjoyed watching. Thank you for creating this. I designed my own preamp / mic processor and ribbon microphone from scratch and it's nice to see youtube has some videos out there like this to help people learn right from the source.
As an EE you should really appreciate the work that has gone into this. had to watch it several times to get some pretty darn good jewels out there.
I really love this series. I'm familiar with Rode microphones, and it's really cool to hear Doug talk about the designs. Thanks again Doug and Dave. Really awesome.
This has been a fantastic series, Dave. Hope to see more from Doug in the future. Maybe you could get some other designers from other companies to discuss the products they've worked on too?
I love this video. Not only does it have a highly informing value, but is also very entertaining.... especially when the two of you have a great genuine laugh about them silly mic customers demanding more excitement in the upper range. I would say that many artists have way too much excitement in their own upper region (brain) anyways.
Thank you for this great video D^2.
Exellent series Doug and Dave. Thankyou, most entertaining and educational. Rhode might be a bit pissed though seeing all their trade secrets explained ):
Doug is a real character
Stuff Rhode, this is fantastically educational ;)
He didn't seem concerned about it, lol
😂😊
@Danny Knapp Because he doesn't work there anymore
Would love to see more videos with Doug. He's a class act, and analog design is a great subject. How about designating a day of the week as "Doug Ford Day"? :)
He's pretty good hey? :)
I watched this video before and after taking my first VLSI design class. After learning to design Opamps from Fets everything in this video makes sense. This might be one of the best displays of a good/real design process on YouTube, everything is organic and logical
Years and several hour-long web searches later, and I think I have found Doug's jFET. Only match I could find is the Solitron FND15. Not a very common part; and I couldn't find that particular topology built from discrete components anywhere.
CIA, you say? A conspiracy theorist might suspect that defense contractors have tried to redact all knowledge of this chip. By the way, we haven't heard anything from Doug in quite a while...
Nice work. I did a bit of searching and found a similar chip. IFD89 by Intergrated Diodes Funnily enough.
He mentioned Siliconix, and their Si1000 are a good match. There's an app note in their 1986 databook on using it for electrets etc. The databook is available on bitsavers.
you should have him come back for more lessons! turn this into a permanent thing?
@Olav Viking Mate, microphones are not used just in music industry.
Yes, please!
@John Yang :}} didn;t expect to read that
I'd love to see more videos with Doug as well !
Ok, so now I added some R0DE mics to my amazon cart :-) Thank you for doing this, and please more content like this. I really appreciate the deeper dives into practical analog
This series is a classic in the making - simple as that. Make sure you back up these vids for posterity
I have an original Rode NT1 (battleship grey version, not the 'A' model), best mic I've ever owned! Great to see the designer behind it and the genius in design. I'd love to see more pro-audio related videos on EEVBlog!
I'm pretty sure the old Rode NT1 is a Jim Williams design and not a Doug Ford's, it also wasn't made by Rode in australia, it was made by 797 audio in china, I believe back when rode started, they didn't make their own mics.
Fantastic video series! I wish I had someone like Doug as a mentor.
thank you for this high quality, free and enjoyable education.
I've watched EEV Blog for years but this is by far the most informative video I've seen! Thank you! Lots of great stuff in this one! Thanks Doug and Dave!
Great tutorial. I haven't designed (active) analog circuits since college.
This is a fantastic series that I had not yet seen. Doug is a good teacher, and his designs are very interesting. Also interesting to hear about production issues/cost savings, etc. Thanks.
How did I miss this? Amazing info download from Doug, thanks for bringing this out for us to learn from. Fantastic.
I think I've watched almost all the videos, but I skipped this series about microphones. But as usual, now I'm very interested in microphone techniques, and this is a gold mine! Thanks, Dave, yet again. The YouTube channel that keeps giving.
Dynamic duo. Bring Doug back. This was informative and fun.
@EEVblog: Even by watching the video again (don't know how many times) I can discover some new details again and again! I also liked the frequency with the little more "woohoo" very much. :-D
That kind of videos are very interesting and very well in teaching electronics basics and circuit design - wouldn't that be good to have some more of those type of videos? Maybe (if you are allowed to) some more out of your field of operations back from your days at other companies?
The one thing I don't like about Dave is that he tries to finish everyone's sentences to show that he's aware of the topics too. This may be due to an insecurity about where his knowledge level is. Other than that, great stuff.
Do white board markers ever work properly? This video brought back memories of lectures in the 90's when lines were drawn, then drawn over again because they were faint, then drawn over a third time before the lecturer said "@#%& it" and threw the marker in the bin. Every lecturer saw two or three white board markers hit the bin :-)
great video, I didn't think you would ever use a power amplifier in a preamp, very interesting topology.
Solved my problems about initiating a design from scratch! Thanks for that 😀
I'm a mining engineer, I'd love to see a very low frequency mic schematic or a tweak to one of those mentioned that allows for very low frequency pickup.
Thank you both ,I love mic design series
I enjoyed learning about the construction of the NT1000 as I've experimented with it before, very easy to make recordings at low volume with this mic, and hardly any gain needed. Now I know why!
learned alot from this series. Thanks. I like to tinker with wide band audio in CB communications. Now I have some better ideas for mic preamps and mic choices.
huge audio enthusiast here so this content with Doug I'm vibing with!
That's an old but nice one with a real deal mike design pro! Very interesting and enlightening. Makes me wish I could work with Doug and learn tons of cool stuff he knows.
35V RMS? Then you just put a step-down transformer on the output, but then I'd just o for an all-tube construction putting the transformer in the plate circuit.
I bet a low-noise +48V to filament and plate converter is perfectly viable especially if you go for a hybrid design where the tube (subminiature, preferably) is there for specific distortion rather than being an amplifying workhorse.
Please, more of these vids with Doug!
What a super series - absolutely fascinating! A big thank-you from me, Dave. I'm curious about one thing. Doug used a JFET in the early part of the video, which I might understand to be because of their high input impedance and low noise (compared to say, a BJT). Would a MOSFET also be ok in that position or is a JFET preferred? Thanks for any light you can shine on this point.
MOSFETs are pretty much all enhancement mode devices, which means the gate sits at a voltage somewhere between the source and the drain and it's a pig to set a reproducible dc bias point.
JFETs, on the other hand are depletion mode devices, and their gates sit at a voltage below the source, making it easier to set a dc bias point, especially if you have a source resistor to stabilise it.
+EEVblog Doug is just awesome, I hope we can get more videos from him soon.
I looked at an NT3 frequency response curve just now and sure enough, there's a bit of a whoohoo! at 6kHz
My god! I would love it if an engineer would write "more excitement in this region" on the data sheet. I dont care what kind of device it is, but thats something that needs to be in a datasheet :)
I find a very low resistor on the emitter of the top pnp going to 15V can sometimes increase stability quite a lot..
What a beautiful mind. I using rode microphones in my studio btw. Thanks for very interesting topic and some topology suggestions, very exciting. Especially at the hi end of frequency response :)
Great stuff, guys - really fascinating stuff.
There is a simple trick to reduce the noise figure. Simply add a voltage divider on the output. Your 12db noise figure will drop to almost nothing.
"Did you stick one until it works ..."
Dave, please don't give away the most important trick in electronics design!
When you run a dynamic mic with the phantom power on it can be hard to sing. Happened to me on a mixer that could only have phantom on or off for all inputs rather than individual inputs.
I love Doug's manner of speech...very interesting...I could listen to him for hours
It's very interesting (comical) watching a couple EEs at work. Very good!
I was just doing research on converting my d104 with tug9 microphone pre-amp / impedance matching circuit to use a FET instead. Love learning theory and better ways to EE. Just a hobbyist though.
'tis always good to hear why something was designed a certain way, not just how it was designed.
Barrios Groupie - 2014-06-19
This series is awesome because Doug knows what he's talking about.